This invention relates generally to hand tools and related manufacturing processes. More particularly, the present invention relates to the manufacture of plastic molded surface protective striking tools, such as hammers and mallets, which permits tool components to be assembled together in a simplified manufacturing process, wherein the components are selected to maximize performance of the striking tool while lowering the costs thereof.
Traditionally, surface protective striking tools, such as soft-faced hammers and mallets, have been manufactured much like other types of striking tools with the exception that the tool head or impact face is made of a material intended to minimize damage to the work being struck. The tool or impact heads have often been made of rawhide, rubber, copper, brass, wood. The particular material chosen for the tool head or impact face has been dependent upon the task to be accomplished.
In the course of time, improvements have been made to the design of traditional surface protective striking tools. For example, surface protective hammers have been devised which utilize a permanent or non-sacrificial handle and head component, and interchangeable and replaceable impact faces which are attachable to a holder provided in the head of the permanent portion of the tool component. Such interchangeable or replaceable faces are made of a wide range of materials, and particularly out of new engineering plastics, which often exhibit superior working characteristics, i.e., they are tougher, softer, more cut resistant, etc., than traditional tool heads for surface protective striking tools. Such modern surface protective hand tools which utilize a non-sacrificial holder and replaceable insert faces have become very popular with professional mechanics and tradesmen but, due to their comparatively high cost, such hand tools are not well used by or known to the semi-professional or home mechanic.
Attempts have been made to design and manufacture tool components, including striking tools, in a more efficient manner while retaining the reliability, durability and performance of hand tools manufactured in traditional ways. Specifically, a variety of plastic encased tool components are generally known in the art, wherein a skeletal core member is contained within a resilient outer encasement or cladding of molded plastic material or the like. The tool component is produced by placing the skeletal core member into a mold cavity which is then filled with a selected thermoplastic molding compound under suitable conditions of heat and pressure. The plastic material is permitted to cure, followed by removal of the plastic encased tool component from the mold cavity. Examples of such plastic encased tool components include elongated tool handles, plastic-faced hammers and mallets, etc.
In the production of tool components of this general type, the skeletal core member must have sufficient structural integrity to withstand the pressures and temperatures encountered in a typical injection molding environment. That is, the core member must be able to retain its structural size and shape throughout the injection molding process, to prevent production of defective tool components. In the past, skeletal core members of solid cross-section have been commonly used in the manufacture of plastic encased tool components. However, since the cost of such tool components is primarily attributable to the cost of materials, it is desirable to reduce or minimize the material used in the skeletal core member to the extent possible without sacrificing the requisite strength. In this regard, reduction in the cross-sectional size of a solid core member is ineffective to reduce material costs, since additional molded plastic encasement material is required to form the finished tool component.
Hollow skeletal core structures have been proposed for use in the manufacture of plastic encased tool components. A hollow member beneficially reduces the material cost in the finished tool component without requiring the use of additional molded plastic encasement material. Moreover, a hollow skeletal core reduces the weight of the finished tool component, resulting in a lightweight tool product which can be especially desirable in certain applications. However, despite the hollow construction of the skeletal core member, a substantial amount of core member material has still been required in order to provide the core member with the necessary structural integrity to withstand injection molding processes.
There exists, therefore, a need for improvements in manufacturing processes for making plastic encased tool components, wherein a hollow core member constructed from substantially minimum material quantities is contained within a resilient outer encasement of molded thermoplastic material or the like. Additionally, there is a need for specialty striking tools, such as surface protective hammers and mallets, which are highly versatile in regard to the material utilized on the impact surface, which retain the reliability, durability and performance characteristics of similar striking tools manufactured in traditional ways, and which have a substantially lower cost of manufacture than such traditional striking tools. Additionally, a need exists for such striking tools which may include a no-bounce feature, without materially increasing costs. The present invention fulfills these needs and provides further related advantages.